Magnetrons

ABSTRACT

In a magnetron of the type wherein an annular anode electrode and a cathode electrode are contained in an interaction space in an evacuated envelope and magnetic flux acting upon the interaction space is produced by a magnet positioned on the outside of the envelope, first and second sealing members are sealed to the opposite ends of the anode electrode to define the evacuated envelope, a first magnet is disposed coaxially with the anode electrode substantially in contact with the outer surface of the first sealing member and a second magnet is disposed coaxially with the anode electrode substantially in contact with the outer surface of the second sealing member.

[451 July 17, 1973 MAGNETRONS [75] Inventor: Tomokatsu Oguro, Mobura City,

Japan [73] Assignee: Hitachi Ltd., Tokyo, Japan [22] Filed: Apr. 26, 1972 [21] Appl. No.: 247,821

[30] Foreign Application Priority Data 1/1966 Hodge ..315/39.71 10/1947 Nelson ..3l5/39.71

Primary Examiner-Rudolph V. Rolinec Assistant Examiner-Saxfield Chatmon, Jr. Attorney-C. Yardley Chittick, Charles E. Pfund et al.

[57] ABSTRACT in a magnetron of the type wherein an annular anode electrode and a cathode electrode are contained in an interaction space in an evacuated envelope and magnetic flux acting upon the interaction space is produced by a magnet positioned on the outside of the envelope, first and second sealing members are sealed to the opposite ends of the anode electrode to define the evacuated envelope, a first magnet is disposed coaxially with the anode electrode substantially in contact with the outer surface of the first sealing member and a second magnet is disposed coaxially with the anode electrode substantially in contact with the outer surface of the second sealing member.

Patented July 17, 1973 3,746,916

4 Sheets-Sheet 3 Patented July 17, 1973 4 Sheets-Sheet 1 F/GB MAGNETRONS BACKGROUND OF THE INVENTION This invention relates to a magnetron and more particularly to a magnetron suitable for use in an electronic range or a microwave oven, a thawing equipment or the like.

In the prior magnetron, since a permanent magnet utilized to create high frequency oscillations is disposed remote from the interaction space of the magnetron, the magnetic flux produced by the permanent magnet is not utilized efficiently so that it has been necessary to use a permanent magnet of large size. Increase in the size of the permanent magnet causes corresponding increase in the size of the magnetron incorporating it with the result that the mounting or the configuration of the radiator for the magnetron is limited when it is incorporated in a microwave oven or the like. In order to obviate this difficulty, although an axial mount type magnetron has been proposed, with this type since the magnetic poles of the permanent magnet are disposed in the envelope of the magnetron there are such problems that the magnetic characteristic is affected according to the material of the magnetic poles and by the heat generated during the operation of the magnetron. Furthermore, the gas released by the magnetic poles causes serious problem.

SUMMARY OF THE INVENTION It is the principal object of this invention to provide an improved magnetron capable of eliminating the difficulties mentioned above.

Another object of this invention is to provide an improved magnetron according to which it is possible to dispose the magnet as near as possible to the interaction space thereby providing a magnetron which can operate efficiently with small size.

Still another object of this invention is to provide a magnetron of a construction in which it is possible to reduce the width of the yoke with respect to the diameter of the anode electrode thereby'enabling to supply cooling air to the magnetron in any direction.'

A further object of this invention is to provide a magnetron with a magnet of small size thereby broadening the space in which the cooling fin can be mounted.

Still further object of this invention is to provide a novel magnetron wherein the magnet is disposed outside of the interaction space of the magnetron which is required to be maintained at an air tight vacuum condition thereby eliminating the problem caused by the gas released from the magnet. I

Yet another object of this invention is to provide a novel magnetron wherein the magnet is disposed remote from the anode cylinder thereby reducing heat conduction from the anode to the magnet and wherein the magnet is disposed outside the envelope thereby decreasing the effect of the radiant heat from the cathode electrode to the magnet.

Another object of this invention is to provide a novel magnetron wherein the magnet is disposed outside of the envelope thereby magnetically shielding the component parts contained therein against a ferromagnetic body, such as an iron sheet situated about the magnetron.

According to this invention there is provided a magnetron comprising an annular anode electrode including a plurality of inwardly projecting vanes, a cathode electrode disposed concentrically with the anode electrode, a first nonmagnetic sealing member sealed to one end of the anode electrode, a second nonmagnetic sealing member sealed to the other end of the anode electrode, the anode electrode and thefirst and second sealing members cooperating to define an evacuated envelope, a first magnet disposed coaxially with the anode electrode ans substantially in contact with the outer surface of the first sealing member, and a second magnet disposed coaxially with the anode electrode and substantially in contact with the outer surface of the second sealing member.

The magnetron is provided with a metal tube extending through the side wall of the annular anode electrode or the bottom of the second sealing member and an output conductor extends through the metal tube.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 shows a longitudinal section of a magnetron embodying the invention;

FIG. 2 shows a sectional view of the magnetron shown in FIG. 1 taken along a line I] ll;

FIG. 3 shows an top plan view of the magnetron shown in FIG. 1;

FIG. 4 is a perspective view of a toroidal magnet utilized in the magnetron shown in FIG. 1;

FIGS. 5 and 6 show perspective views of two types of the yoke utilized in the magnetron shown in FIG. 1 and FIGS. 7 and 8 show a longitudinal view of a modified magnetron embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIGS. I to 3 of the accompanying drawing, the magnetron shown therein comrpises an annular anode electrode 10 including a plurality of radial vanes 11, a first sealing member 12 hermetically connected to the upper edge of the anode l0 and including a central cylinder 14 extending upwardly, and a second sealing member 13 hermetically connected to the lower edge of the anode, the sealing member 13 being provided with an exhaust tube 33 and ametal tube 25 for passing an antenna conductor 27 to the outside on the bottom thereof at positions remote from the central axis. For the purpose of decreasing the leakage of the magnetic flux produced by the magnet to be described later thereby efficiently supplying the flux to the interaction space, the first and second shielding members 12 and 13 are made of thin metal sheets of low permeability or having a characteristic of being saturated at a low fluxdensity such as copper alloys Monel metal or constantan, for example, or copper or the like. A first magnet of toroidal form 15 is disposed to surround the cylinder 14 of the first sealing member 12 for embracing the cylinder 14. In the interaction space is disposed a cathode electrode 18 concentrically with anode 10, the cathode electrode being supported by a cathode support 19. The upper end of cathode support 19 protrudes upwardly to form a cathode terminal 20 beyond the upper end of a cylindrical insulator bushing 17 connected to the upper end of cylinder 14 of the first sealing member 12. The cathode support 19 is supported by a rod 21 extending through an insulator disc 22 overlying the flattened upper end of the support 19. In this embodiment, anode electrode 10, cylinder 14 and cathode electrode 20 are arranged in concentric relation. A cylindrical second magnet 16 is disposed on the under surface of the second sealing member 13 in concentric relation with the interaction space 100. Yokes 23 and 24 of iron plates are provided to fix in position the component parts of the magnetron described above and to form a closed magnetic circuit for the first and second magnets 15 and 16. A metal fixture 28 is connected to the lower end of the metal tube 25 depending from the second sealing member 15 through a cylindrical insulator bushing 26, the metal fixture being electrically connected to the lower end of copper rod 27 adapted to transmit the electromagnetic energy generated in the interaction space 100 thereby acting as an antenna. A flange 29 is connected to the metal tube 25 to receive a gasket 30 for facilitating the electrical connection to an external load (not shown).

As shown in FIG. 4, in the preferred embodiment of this invention, the toroidal magnet 15 comprises two halves 15a and 15b. Furthermore, as shown in FIG. 5, the yoke 24 takes the form of a flat rectangular plate with a notch 24a at the center of one longitudinal edge and extending towards the center of the plate for receiving the metal tube 25 depending from the second sealing member 13. The yoke 24 is formed with a plurality of openings 24b through 24e used to secure the yoke.

As shown in FIG. 6, yoke 23 comprises two identical halves 23a and 23b, each having vertical portions, upper horizontal portions and bottom horizontal portions which are secured to the upper surface of horizontal yoke 24. The upper horizontal portions are provided with semicircular notches 23c and 23d adapted to receive metal tube 14 of the first sealing member 12 and the bottom horizontal portions are provided with threaded openings 23e and 23f for receiving screws used to secure the yoke 23 to the horizontal yoke 24.

As can be noted from FIG. 3, the width of the yoke 23 is designed to be smaller than the diameter of anode electrode 10.

FIG. 7 illustrates a modified magnetron wherein the output of magnetron is taken out from one side of the anode electrode. For the sake of clearness, yokes are not shown in FIG. 7 and component parts identical to those shown are designated by the same reference numerals. In this embodiment, anode cylinder 34 comprising anode electrode has a longer length than that shown in FIG. 1 and metal tube 25 is secured to anode cylinder 34 in the radial direction thereof. Since the axial length of the anode cylinder 34 is increased, the bottom of the second sealing member 13 is raised or depressed inwardly so as not to decrease the effective magnetic flux acting in the interaction space 100.

Although in the embodiments shown in FIGS. 1 and 7, the cathode support 19 and the cylinder 14 of the first sealing member 12 are shown to coaxially extend in the vertical direction, it is also possible as shown in FIG. 8 to construct the first sealing member 12 in the form of a cup like the second sealing member 13 and to cause the cathode supports 19a, 19b to extend through the anode cylinder 34 or the sealing member. Then it is possible to use a first magnet 16a in the form ofa cylinder like the second magnet 16 thereby miniaturizing the magnetron.

It should also be understood that the distribution of the magnetic flux acting upon the interaction space can be adjusted by varying the height or the cross-sectional area of the magnets and that the flux distribution can be improved by mounting ferromagnetic metal plates on the inner surface of the first and second sealing members near the interaction space.

It will be clear that many other changes and modifications will be obvious to one skilled in the art without departing the true spirit of the invention as defined in the appended claims.

What is claimed is:

l. A magnetron assembly comprising an evacuated discharge device having an annular anode electrode including a plurality of inwardly projecting vanes, a cathode electrode disposed concentrically with said anode electrode, a first nonmagnetic thin-wall sealing member sealed to one end of said anode electrode, a second nonmagnetic thin-wall sealing member sealed to the other end of said anode electrode, said anode electrode and said first and second sealing members cooperating to define an evacuated envelope with said thin-wall sealing members opposed and closely spaced to the axial ends of the interaction space between said anode and cathode electrodes; a first magnet disposed coaxially with said anode electrode with a first surface substantially in contact with the outer surface of said first sealing member; a second magnet disposed coaxially with said anode electrode with a first surface substantially in contact with the outer surface of said second sealing member; and a ferromagnetic yoke extending from the opposite surfaces of said first and second magnets to support said assembly and provide a closed return magnetic circuit for said first and second magnets.

2. The magnetron according to claim 1 wherein said first sealing member is provided at its center a cylinder extending coaxially with said anode electrode and said cathode electrode is supported by a cathode support axially extending through said cylinder.

3. The magnetron according to claim 1 wherein said first sealing member is provided with a cylinder laterally extending from the side surface of said first sealing member and said cathode electrode is supported by a cathode support axially extending through said cylinder.

4. The magnetron according to claim 2 wherein said first magnet takes the form of a toroid encircling said cylinder of said first sealing member.

5. The magnetron according to claim 1 wherein said second sealing member is provided with a metal tube for deriving the output of said magnetron on the bottom surface thereof at a position remote from the axial center.

6. The magnetron according to claim 1 wherein said anode electrode is provided with a metal tube extending through the side wall of said anode electrode for deriving out the output of said magnetron.

7. The magnetron according to claim 6 wherein the bottom of the second sealing member is depressed inwardly of said envelope and said second magnet is placed in said depressed bottom in contact therewith.

8. The magnetron according to claim 1 wherein both said first magnet and said second magnet are in the form of a cylinder.

l l I 4 

1. A magnetron assembly comprising an evacuated discharge device having an annular anode electrode including a plurality of inwardly projecting vanes, a cathoDe electrode disposed concentrically with said anode electrode, a first nonmagnetic thin-wall sealing member sealed to one end of said anode electrode, a second nonmagnetic thin-wall sealing member sealed to the other end of said anode electrode, said anode electrode and said first and second sealing members cooperating to define an evacuated envelope with said thin-wall sealing members opposed and closely spaced to the axial ends of the interaction space between said anode and cathode electrodes; a first magnet disposed coaxially with said anode electrode with a first surface substantially in contact with the outer surface of said first sealing member; a second magnet disposed coaxially with said anode electrode with a first surface substantially in contact with the outer surface of said second sealing member; and a ferromagnetic yoke extending from the opposite surfaces of said first and second magnets to support said assembly and provide a closed return magnetic circuit for said first and second magnets.
 2. The magnetron according to claim 1 wherein said first sealing member is provided at its center a cylinder extending coaxially with said anode electrode and said cathode electrode is supported by a cathode support axially extending through said cylinder.
 3. The magnetron according to claim 1 wherein said first sealing member is provided with a cylinder laterally extending from the side surface of said first sealing member and said cathode electrode is supported by a cathode support axially extending through said cylinder.
 4. The magnetron according to claim 2 wherein said first magnet takes the form of a toroid encircling said cylinder of said first sealing member.
 5. The magnetron according to claim 1 wherein said second sealing member is provided with a metal tube for deriving the output of said magnetron on the bottom surface thereof at a position remote from the axial center.
 6. The magnetron according to claim 1 wherein said anode electrode is provided with a metal tube extending through the side wall of said anode electrode for deriving out the output of said magnetron.
 7. The magnetron according to claim 6 wherein the bottom of the second sealing member is depressed inwardly of said envelope and said second magnet is placed in said depressed bottom in contact therewith.
 8. The magnetron according to claim 1 wherein both said first magnet and said second magnet are in the form of a cylinder. 